Centrifugal basket construction



Patented 5, 1935 states when rarest was I Western States MachineEompazoy, halt City, iii-ah, a corporation oi t'ltah ApplicationFebruary 25, i933, serial No, Gdfidl This invention relates to basketsfor centrifugal separators oi the type. used in the manufacture ofsugar, starch and various chemicals and is intended to provide aconstruction of basket that shall be free from faults inherent in thetype or construction that has previously been known and used in suchcentriiugals.

According to the practice heretofore followed a perforated metallicsheet of appropriate length and thickness was rolled into cylindricalform and its abutting edges were fastened together by means of buttstraps. The perforations in the sheet extended close to the top andbottom edges and were arranged in circumferential perforated areasseparated by intermediate circumferential areas that were leftimperforate for the reception of external reenforcing hoops. Saidabutting ends were fastened together by a series of vertically spacedbutt straps which were curved strips of sheet material as thick,- orthicker than the basket wall overlapping the perforated areas forseveral inches on each side of the joint or crack in the basket wall.These straps were se- 4 cured to the wall by multiple rivets passed 25through perforations in their ends that were in registry withcorresponding perforations in the basket wall. To balance the basket, itwas necessary to apply two additional sets of similar straps 12c degreesfrom the butt straps and res,- tened to the basket also by rivets.

The top and bottom elements of the basket were then applied to thecorresponding edges of the. basket wall in lappedrelation thereto andwere .fastened to it by bolts, pins or rivets. The

35, reeniorcing hoops passed between the individual straps of each rowof butt straps.

For many years the baskets in use have been.

of this type of construction, although it was recognized that theiroperation in service was attended by a very considerable waste ofmaterial being treated. Notmnly were thebaskets subiect to leakagearound the top and bottom edges of their filter linings, but miles thesugar being centrifuged was subjected to excessive applicapicks up thescum) the loss'of sugar averages seven pounds for each pound of hotwater applied; Moreover, imperfect drainage prolongs tion of wash waterthere would be found rings (or. ere-rs) Q the purging period, that is,the centrifugal extraction of the original syrup or liquor with whichthe grains were mixed, and makes the washing operation longer and moredifiicult.

' After careful study or" andexperiment with 5 centrifugals inattempting to learn the causes of these troubles, I have discovered thatthe large percentage of waste involved in the operation of suchcentrifugal baskets was due to,several faulty features of construction,whose disadvan- 1o tages have been entirely overlooked heretofore. Theimportance of uniform drainage throughout the whole perforated area ofthe basket wall has not been appreciated or, if it has been, no

basket construction has been provided to secure :15 that advantage. Inthe first place, the use of butt straps and counterbalance straps, aswell as the use of overlapping flanges forming top and bottom rivetedjoint connections with the basket wall, has resulted in doubling thethickness of the basket wall at such locations with the consequencethattlie depth or radial length of the outlet perforations in the doublethickness areas was alsodoubied. Careful tests have shown-me that theselonger outlet perforations tend to gum up or accumulate sticky materialuntil their dis "charge capacity is very greatly reduced. In addition tothis, some of the holes are closed by the attaching rivets. Therefore,substantial areas ofthe basket wall will have less than half so thefreedom of drainage that equal areas in other parts of the basket have.The result is that after purging and moderate washing there willbefound. discolored streaks and patches of sugar, which are highlyobjectionable asisuch sugar is of inferior grade. .Oh the other hand, ifthese discolored areas are washed out by suficient washing the portions0! the sugar wall having freer drainage become excessively washed,involving excessive wastage, which is I also highly uneconomical andobjectionable.-

'{By means of the construction hereinafter described I have eliminatedperforated areas of double thickness of basket. walland have alsoeliminated the'use of fastening rivets which have 5 been used forfastening overlapped perforated members together and which necessarilyclose a considerable number of such perforations and have therebysecured, for the first time in this art, a perforated centrifugal basketfor sugar cenia'iiugals and the like, which have uniformly. spacedoutlet periorations of uniform depth 61- radial length so that allportions of the perforatedareaofthebasketwallpossessequaldrain- I agefacilities, thereby avoiding the occurrence 56 tion of washwater,largely reducing previous wastage. Moreover, by reason of the equ l andfree drainage thus secured, the purging can be accomplished'moreperfectly and more quickly than before, which of itself aids indispensing with the use of considerable quantities of wash water, sincemuch of the scum is carried off by the freely flowing liquor or syrupextracted in the first portion of the runbefore the wash spray isapplied.

top and bottom edges of the basket filter linings is avoided by spacingthe top and bottom rows of perforations a substantial distance from thetop and bottom elements, thereby providing a smooth unbroken surface ofsufficient extent to form an adequate support for the salvage edgedlinings with which these smooth unbroken top and bottom margins orselvage areas of the hasket wall form an effective seal permitting theuse'of linings that are slightly shorter in verticalheight than thevertical distance between the top and bottom elements next to the basketwall. Besides providing aperfect sealing seat for the top andbottomedges of the these smoothunbrokenselvage areas serve to prolongthe life of the fine linings, since in being crowded tightly against thetop and bottom in the effort toprevent leakage of material at thosepoints they become bent and crumpled at their edges under pressureexerted by the discharger I plow, which is a prolific source of damageto. the linings. Moreover, the selvage margin areas of the basket wallafford a much stronger and more reliable joint with the top and bottomelements of the basket than was obtained by previous constructions;

.Theseand other features of theinvention will.

- be particularly described in the following speck fication and'will bedefined in the claims hereto annexed. In the accompanying drawing I haveillustrated a preferred form embodying the principles of this invention,in which Fig. 1 isa side elevation, partly in central section, of myimproved basket construction showing the basket'in its relation to: thesurrounding curb or casing.

Fig. 2 is a detail showing in perspective on a larger scale the jointbetween the bottoms and the basket wall and illustrating the calibrationof the bottom for the purpose of ascertaining the thickness of the sugarwall as the basketis beingloadedr' 2' a Fig. 3 is an enlarged detail.showing a vertical section through the upper portion of the basket walland top.

. mg. ais a detail showing in when on as same scale as Fig. 3 thearrangement of perfora-' tions of the basket wall.

4 is an enlarged detail in plan of the abut ing ends "of the sheetforming the peripheral wall with their-uniting weldingfseam In'thepractice of this invention I avoid double thickness of the perforatedareahof the basket wall by elimination of the butt straps and counand ofoverlapping joints having outlet perforations by making the basket ofintegral consu-uction.:'the eby u ing uniform dcpth of the outletperforations and distribution or spacing'Tof such t-the perforatedpreaof'tfuev mama and rapid'drainageis-af construction and arrangement bywhich these important advantages are secured. The suspension shaft 1 ofthe centrifugal, according to usual practice, is provided at itslowerend with r a frusto-conical enlargement 2 and a downward extension2 of reduced diameter for the purpose 7 of receiving the hub 6concentric with the ra- Waste of material through leakage around theable to shorten the vertical depth of the peripheral ring'7'sufiiciently'to allow-this ring, when the basket gyrates, to swingover the top of the.

interior flange 20 bounding the central discharge opening in the bottom20* of the curb or casing. This upward inclination of the spider 5-,with the corresponding-thickening of the hub and peripheral ringthereof, makes it possible to provide a collecting trough or ring forthe bottom of the curb or casing of much -greater width than waspracticable with previous constructions in this type of centrifugalwithout sacrifice of strength.

The perforated'basket wall 10 comprises a metallic sheet provided withuniformly spaced and dimensioned perforations throughout the wholeperforated area of the basket, while at the same time providing at thetop and bottom marginal portions of the basket wall selvages orimperiorate' areas 10 and 10 for the reception of my selvage edge liningor backing, which forms the. subject matter of -a companion application,and

prevents leakage of the material around the lin-- ings at the top andbottom edges thereof. Not onlyis the pitch or center to center distancefrom. one perforation to the next in the same row of perforations thesame, but the pitch or distance from center to center of successive rows.of perforations is also uniform throughout and in consequence thereofthere is uniform and equal drainage throughout the basket fortheescapevof the centrifugally extracted liquid. Furthermore, I

the radial depth of all perforations in the basket is uniformthroughout, since there are no rows of butt straps secured to the basketwall and rivetsplugging a substantial number'of the perforations byreason of the construction that will now be explained.

The perforated sheet is rolled into cylindricalv form and its opposingends" are cut of! true and even and bevelled at their edges, and arethen drawn tightly together by circumferential clamps provided with drawbolts. These abutting endssheet 10, while the shell is held in cylin-'drical form, are then welded together throughoutthelemth of the seamfrom top to bottom, thus making an integral connection between. the twoends. The inside and the outside "of the welded seam are then.groundsmooth. v a

The top and bottom edges of the integral cylin vdrical sheet to'form thebasket wall are then turned to form'a snug fit with the top and bot--tdm'elements of the basket; the bottom is then forced into the inside ofthebottom'edge until its outer'odgelies flush with the bottomedge of thetop 12 isthen crowded Over the top edge against intervening verticalspacers and the top and bottom are then drawn together against theintervening spacers to secure exact parallelism as well as properengagement with the edges of the basket-wall." When thus exactlypositioned with reference to each other and to the basket wall, the topand bottom elements are. exactly 'equi-di'stant from each other allaround the basket and a continuous welded seam is made between thebottom and top elements while they are held in that relation. In thecase of a steel basket, the continuous welded seat at top and bottomwill preferably be formed by arc welding. In case of bronze or similaralloys the welding is preferably done by oxy acetylene methodof welding.

The hoops 13 are turned or machined inside to slightly smaller dimensionthan the periphery of the basket wall and are then heated and forcedover the basket wall in proper spaced relationship insured by temporaryspacers. These hoops are shrunk tightly on the basket wall by coolingand are held against accidental displacement by spot welding atintervals around the basket wall, as shown at 13 such spot weldingpreferably being made alternately on the top and bottom sides of thehoops. The bottom hoop is the last to be applied and after itsapplication is integrally welded to the bottom marginal portion of the Vbasket wall by a continuous welding seam ex-.

tending entirely around the bottom. As the besket bottom has alreadybeen integrally united with the inside face of the lower edge portion ofthe basket wall by a continuous welding seam, asabove explained, thiscontinuous welding of the bottom hoop forms, in efiect, a peripheralintegral extension of the bottom member and there fore the shocks,caused by its impact against the surrounding wall oi the curb or casingas the basket gyrates or sways, are transmitted directly to the basketspindle and there is no danger of the hoop becoming loosened anddropping ofi, which occasionally happens with consequent -damage to thebasket when the hoop is secured I in strength but which efiects a muchmore complete and satisfactory drainage than in the-case of previousconstructions, and also makes provision for the elimination of leakageof material to be purged around the top and bottom edges and permittingthe use of a collecting trough for the liquid oi any desired widthinstead of being restricted to the narrow widths heretofore necessitatedby previous constructions. There are no rivets to shear or to clogdrainage openings and no butt straps to impair complete ef iciency ofdrainage.

The outer portion 8 of the basket bottom 4. is provided with a series ofaccurately spaced gauging grooves or rings 4 so that the centrifugaloperator or attendant guided accurately in loading the basket. Thesecalibrating or gauging rings at will preierably be located an inchapart, the outer one of these being one inch, or unit of measurement,from the inside of the basket wall, so that if it is known that theinner ring of any given basket, for example, is 7 inches away from thebasket rial 4 it is desired to load some parinches and correspondinglyany other desired thickness may be indicated by similar manner, thusenabling the operator to load to any desired thickness of wall accordingto the material that is being purged. A further important advantage ofthe visible calibrating of the basket bottom is that it makes possiblethe accurate ascertainment of the amount of shrinkage in the thicknessof the bottom portion of the sugar wall, thereby affording a check onexcessive washing or leakage of material. When the material being centriiuged is loaded into the basket it builds up into a vertical annularwall inside of the outside wall of the basket andnormally this walled upring oi material is thicker at the bottom than at the middle and topportions and therefore should re ceive a slightly greater supply oi?wash fluid than the upper portions of the walled up ring receive..Thereiore, by providing a calibrating means on the bottom the shrinkagecan be checked up -for the purpose of determining precisely. how muchmore spraying is required over this area and also to detect'the fact ofover-spraying which will cause excessive shrinkage and consequent waste.s

In actual practice I have made the imperiorate marginal portions 10 and10 of the perioratedbasket wall at top and bottom approximately one-halfinch in width, or a little wider than the diameter of the outletperforations, although this dimension is not prescriptive. These smoothmarginal or salvage areas the basket wall atford a smooth uninterruptedannular seat at top and bottom iormlng'a continuous sealing support forthe upper and lower selvage edges of the basket filter linings. This isimportant because baskets, as previously constructed with the top andbottom rows of outlet perforations very close to the top and bottomelements of the basket, I have found are a prolific source of leakage ofmaterial at these points. Furthermore, in the attempt to lessen leakageit has been customary to endeavor to fit the finely perforated filterlinings snugly between the top and bottom walls with the result thatthis fine lining has become curled up or distorted under the pressure ofthe discharger plow so that leakage oi material at both top and bottomoccurs. en the above described marginal selvages are used, it isunnecessary to have the finely perforated filter lining fit snuglybetween the top and bottom of the basket and the 2 may be made slightlyshorter than the vertical distance between top and bottom to allow forexpansion and as the sealing at topand bottone is effected by the smoothcontact of the selvage portion or" the outer lining or backing withthese smooth salvage areas 0?": tr e basket wall, leakage presented andthe life or duration of trifugals in operation. To get the fullestadvantage of these imperiorate salv ge areas 1 have devised an improvedbasket iinug havin top and bottom sealing sel /ages, but such ovedlining forms the subje t matter of and-Aer copending application filedby me.

By shortening the outer ring oi the bottom spider h compensatingthickening of the ring, new baskets of this on in wide trough v diameter2ok while 4 the collecting trough of the curb to an undesirable extent.

metallic sheet bent into cylindrical form with its abutting end edgesintegrally welded together and having uniformly spaced outlet openings,all of which are of equal radial depth throughout whereby equal anduniform drainage is afforded for the escape of the. centrifugally extracted liquid from the walled up material in the basket.

, 2; A centrifugal basket of the type described comprising a perforatedperipheral wall of uniform thickness" throughout, thereby .providingoutlet perforations of uniform depth radially of the basket, and top andbottom elements 'united therewith, the top and bottom rows ofperforations being spaced a substantial distance from said top andbottom elements to leave a smooth unbroken annular selvage area ofadequate width to form a smooth sealing contact with the subby providinga perforated wall of uniform thickness having outlet perforations ofequal radial depth throughout, and top and bottom elements ofappropriate form united to the top ,and bottom edge portions of saidwall.

- 4. A centrifugal basket of the perforated wall type embracing aperforated cylindrical basket wall of uniform thickness throughout, comping a metallic sheet bent into cylindrical form with its end edgesintegrally united in abuttingrelationship, thereby providing. outletperforations of equal depth uniformly spaced apart, top and bottomelements united thereto by continuous welding seams, and a series ofvertically spaced external reenforcing hoops secured around the basketwall and held in fixed spaced relationship to each other by spotwelding.

EUGENE RonERTs.

